Neurons in the external nucleus of the inferior colliculus (ICX) of the barn owl undergo experience-dependent plasticity in their tuning for interaural time difference (ITD). Little is known about the mechanisms underlying this learning process. The primary goal of this research is to study the role played by GABAergic inhibition in experience-dependent plasticity. Iontophoretic techniques will be used to block GABAergic inhibitory input to ICX neurons in prism-reared owls. The contribution of GABAergic inhibition will be evaluated by assessing changes in ITD tuning curves before and after blocking GABAergic inhibition. The second goal of this research is to use auditory training to potentiate ITD-specific synaptic transmission to ICX neurons after blocking GABAergic inhibition by iontophoretic application of biocuculline. The molecular mechanisms that mediate this plasticity will then be explored. Results from these studies will contribute to our understanding of the neural mechanism that underlies experience-dependent plasticity in the vertebrate brains.